As this kind of switch, for example, a terminal seal structure used in a switch device, such as an electromagnetic contact, a switch, or a timer, described in PTL 1 is known. In the seal structure, a seal case in which a contact mechanism can be housed and a seal cover which closes the top of the seal case, are formed of a seal case block made of a metal. Further, the seal structure is a terminal seal structure wherein a pair of insertion holes into which the connection terminals of a contact mechanism block are inserted, are formed in the seal cover, and sealing is provided by injecting and solidifying a seal material in a condition in which the connection terminals are inserted in the pair of insertion holes. Also, the thermal expansion coefficient of the seal material is set to be equal to or higher than the linear expansion coefficient of the seal case block by adding an inorganic filler to a liquid thermosetting polymer.